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Nasl. z nasl. zaslona. Opis vira z dne 21. 6. 2023. Bibliografija: str. 11-12. Abstract.

Nasl. z nasl. zaslona. Opis vira z dne 16. 5. 2023. Bibliografija: str. 16-18. Abstract.

Nasl. z nasl. zaslona. Objavljeno na spletu: 20. 3. 2023. Opis vira z dne 17. 4. 2023. Bibliografija: str. 1236–1237.

Nasl. z nasl. zaslona. Opis vira z dne 9. 1. 2023. Št. članka: 120916. Bibliografija: str. 7. Abstract.

Finding a maximum clique is important in research areas such as computational chemistry, social network analysis, and bioinformatics. It is possible to compare the maximum clique size between protein graphs to determine their similarity and function. In this paper, improvements based on machine learning (ML) are added to a dynamic algorithm for finding the maximum clique in a protein graph, Maximum Clique Dynamic (MaxCliqueDyn; short: MCQD). This algorithm was published in 2007 and has been widely used in bioinformatics since then. It uses an empirically determined parameter, Tlimit, that determines the algorithm’s flow. We have extended the MCQD algorithm with an initial phase of a machine learning-based prediction of the Tlimit parameter that is best suited for each input graph. Such adaptability to graph types based on state-of-the-art machine learning is a novel approach that has not been used in most graph-theoretic algorithms. We show empirically that the resulting new algorithm MCQD-ML improves search speed on certain types of graphs, in particular molecular docking graphs used in drug design where they determine energetically favorable conformations of small molecules in a protein binding site. In such cases, the speed-up is twofold.

Tailings of old mines often contain metals, which were not of economic interest or could not be recovered with the existing technology at the time of active mining. This is especially true for metals that often occur as by-products in Cu-Pb-Zn-(Ag-Au) ores as Sb, Mo, Ge, and In. A fundamental characterization of some tailings is presented in terms of their mineralogy and content of valuable metals which could be extracted to finance a possible remediation and improve the supply of the EU with critical metals. Tailings from active and abandoned mines in Serbia (Bor, porphyry Cu/Au; Krivelj, porphyry Cu/Au; Blagodat, hydrothermal Pb-Zn; Lece, epithermal Au; Rudnik, hydrothermal/skarn Pb-Zn) and North Macedonia (Sasa, Pb-Zn; Probištip, Pb-Zn; Bučim, porphyry Cu; Lojane, fault-bound vein-type low-temperature As, Sb, Cr at the contact of rhyolite and serpentinite) were studied. Analysis for major and trace elements used a multi-method approach (lithium borate fusion and ICP-MS/OES analysis, gravimetric analysis, instrumental neutron activation analysis, total digestion ICP-OES, infrared spectroscopy) with mineral identification by scanning electron microscopy. Concentrations of the major commodity elements (Cu, Pb, Zn, Au, Ag) varies within several orders of magnitude depending on mineralogy and ore type. Critical metals (Co, Ga, Ge, Sb) contents are low with some exceptions. Some tailings contain moderate to elevated potentially toxic element levels (As, Cd, Pb, Tl). For the sample from Probištip which yielded the highest valuable metal concentrations (>5000 ppm Pb, 4020 ppm Zn), a heavy mineral concentrate of the sand size fraction (0.06 mm to 0.5 mm) was produced and analyzed by SEM and LA-ICP-MS for additional rare phases and trace elements. In all tailings studied, additional milling would be needed to separate ore from gangue minerals. Increasing metal prices might facilitate feasibility studies for some of the localities in the future, despite the limited quantitative information about the characterized tailings.

Summary Mutations causing amyotrophic lateral sclerosis (ALS) often affect the condensation properties of RNA-binding proteins (RBPs). However, the role of RBP condensation in the specificity and function of protein-RNA complexes remains unclear. We created a series of TDP-43 C-terminal domain (CTD) variants that exhibited a gradient of low to high condensation propensity, as observed in vitro and by nuclear mobility and foci formation. Notably, a capacity for condensation was required for efficient TDP-43 assembly on subsets of RNA-binding regions, which contain unusually long clusters of motifs of characteristic types and density. These “binding-region condensates” are promoted by homomeric CTD-driven interactions and required for efficient regulation of a subset of bound transcripts, including autoregulation of TDP-43 mRNA. We establish that RBP condensation can occur in a binding-region-specific manner to selectively modulate transcriptome-wide RNA regulation, which has implications for remodeling RNA networks in the context of signaling, disease, and evolution., Graphical abstract, Highlights • TDP-43 mutants affect condensation properties to a similar extent at multiple scales • Binding-region condensates form on long RNA regions with dispersed UG-rich motifs • RBPchimera-CLIP indicates homomeric interactions promote molecular-scale condensates • Condensation selectively tunes the regulatory capacity of TDP-43; e.g., autoregulation, The condensation propensity of an RNA-binding protein tunes its binding to specific RNA regions across the transcriptome and affects its RNA processing functions. Formation of these “binding-region condensates,” promoted by specific motif types that are dispersed across long RNA regions, expands the ways in which RNA binding can be selectively controlled beyond canonical RNA-binding domains.

Experimental work is an important component of science subjects at all educational levels. The implication of green chemistry ideas indicated the need for optimization of traditional experimental work by implementing green chemistry principles to promote sustainable development. The aim of the study is to present findings from a systematic literature review on the use of experimental work in science education from green chemistry perspectives in the literature from 1995 to 2020. Thus, three electronic databases were reviewed following the Preferred Reporting Items for Systematic Reviews (PRISMA) guidelines. The literature search identified a total of 1199 papers from Web of Science (N = 419), Scopus (N = 578), and Education Resources Information Center (ERIC) (N = 202). After applying inclusion/exclusion criteria, 263 papers were obtained and then analyzed in further detail. The findings highlighted trends in the integration of green chemistry principles into experimental work from primary to tertiary education levels and identified a literature gap, as well as the challenges and the possibilities for future development. The review outlined various opportunities for active learning within experimental work from green chemistry perspectives using a range of methods, with a particular focus on practical, hands-on, and laboratory activities.

The Eighth Central European Conference “Chemistry towards Biology” was held in Brno, Czech Republic, on 28 August–1 September 2016 to bring together experts in biology, chemistry and design of bioactive compounds promote the exchange of scientific results, methods and ideas and encourage cooperation between researchers from all over the world. The topics of the conference covered “Chemistry towards Biology”, meaning that the event welcomed chemists working on biology-related problems, biologists using chemical methods, and students and other researchers of the respective areas that fall within the common scope of chemistry and biology. The authors of this manuscript are plenary speakers and other participants of the symposium and members of their research teams. The following summary highlights the major points/topics of the meeting.

The enzyme-catalyzed degradation of the biogenic amine serotonin is an essential regulatory mechanism of its level in the human organism. In particular, monoamine oxidase A (MAO A) is an important flavoenzyme involved in the metabolism of monoamine neurotransmitters. Despite extensive research efforts, neither the catalytic nor the inhibition mechanisms of MAO enzymes are currently fully understood. In this article, we present the quantum mechanics/molecular mechanics simulation of the rate-limiting step for the serotonin decomposition, which consists of hydride transfer from the serotonin methylene group to the N5 atom of the flavin moiety. Free-energy profiles of the reaction were computed by the empirical valence bond method. Apart from the enzymatic environment, the reference reaction in the gas phase was also simulated, facilitating the estimation of the catalytic effect of the enzyme. The calculated barrier for the enzyme-catalyzed reaction of 14.82 +/- 0.81 kcal mol(-1) is in good agreement with the experimental value of 16.0 kcal mol(-1), which provides strong evidence for the validity of the proposed hydride-transfer mechanism. Together with additional experimental and computational work, the results presented herein contribute to a deeper understanding of the catalytic mechanism of MAO A and flavoenzymes in general, and in the long run, they should pave the way toward applications in neuropsychiatry.

Organocatalyzed ring-opening polymerization (ROP) of e-caprolactone (CL) and 4,4′-bioxepanyl-7,7′-dione as a bis-lactone cross-linker was performed within the oil-in-oil high internal phase emulsions (HIPEs) at 50 °C. In this way, the cross-linked poly(e-caprolactone) (PCL) polyHIPE foams of ∼85% porosity were synthesized. Thermomechanical properties of the prepared polyHIPEs were studied and proved to greatly depend on a degree of PCL cross-linking. The melting and crystallization temperatures as well as the degree of crystallinity of PCL polyHIPE foams decrease with an increasing cross-linking degree. Semi-crystalline polyHIPEs demonstrate shape memory behavior with excellent shape fixity and shape recovery. At an appropriate degree of PCL cross-linking, the polyHIPE temporary shape can be fixed at room temperature, while a transition to the permanent shape occurs upon heating at 40 °C. Moreover, a two-way shape memory behavior of the PCL polyHIPEs under constant stress was observed.

Despite the fact that the methanol synthesis process includes industrially some of the most important catalytic chemical reactions, it is still not clear how different gaseous species impact cataly...

While the function of enzymes has been well-known to researchers for decades, the driving force behind it is still a hotly debated topic. Herein, we report significant evidence for electrostatics being that driving force, using a simple, computationally inexpensive, multiscale model of monoamine oxidase A and phenylethylamine. We found that electrostatics provided by the enzyme substantially enhances the reaction by all the considered criteria (lowering the energy barrier, increasing charge transfer, decreasing the highest occupied molecular orbital–lowest unoccupied molecular orbital (HOMO–LUMO) gap, increasing the dipole moment). The catalytic effect can be rationalized by the stabilizing interaction between the dipole moment of the reacting moiety and the electric field exerted by the charged environment. Both the dipole moment and the electric field are perceivably larger in the transition state as compared to the state of reactants; hence the transition state is stabilized to a larger extent and bett...

Semi-interpenetrating polymer networks (semi-IPNs) were prepared by in situ simultaneous orthogonal polymerizations, where the linear poly(e-caprolactone) (PCL) was synthesized by ring-opening polymerization of e-caprolactone and the poly(styrene-co-divinylbenzene) (PS) network was formed by free-radical polymerization of styrene/divinylbenzene. Semi-IPNs were used as the precursors for the preparation of porous PS monoliths. To this end, the PCL domains were selectively removed by hydrolysis under basic conditions. By changing the amount of organocatalyst used for the ring-opening polymerization of e-caprolactone, the relative polymerization kinetics of both monomers was varied, which has a pronounced effect on the morphology of thus-obtained PS frameworks.

Methane is the central component of natural gas, which is globally one of the most abundant feedstocks. Due to its strong C–H bond, methane activation is difficult, and its conversion into value-added chemicals and fuels has therefore been the pot of gold in the industry and academia for many years. Industrially, halogenation of methane is one of the most promising methane conversion routes, which is why this paper presents a comprehensive review of the literature on methane activation by halogenation. Homogeneous gas phase reactions and their pertinent reaction mechanisms and kinetics are presented as well as microkinetic models for methane reaction with chlorine, bromine, and iodine. The catalysts for non-oxidative and oxidative catalytic halogenation were reviewed for their activity and selectivity as well as their catalytic action. The highly reactive products of methane halogenation reactions are often converted to other chemicals in the same process, and these multi-step processes were reviewed in a separate section. Recent advances in the available computational power have made the use of the ab initio calculations (such as density functional theory) routine, allowing for in silico calculations of energy profiles, which include all stable intermediates and the transition states linking them. The available literature on this subject is presented. Lastly, green processes and the production of fuels as well as some unconventional methods for methane activation using ultrasound, plasma, superacids, and light are also reviewed.

A new species’ class of Cu-, Ga- and Zn-based rate catalysts was prepared by a systematic co-precipitation technique at the different related pH values (6.5–8.0) along with calcination functional conditions, influencing components’ physical properties, these were characterized, and their application performance for water–gas shift (WGS) reaction was researched. Substances were analysed by various experimental methods, namely chemisorption, temperature-programmed reduction (TPR) characterisation, diffraction, physisorption and microscopy. A homogenous size dispersion of the compounds with smaller granular particles was obtained for catalysis, implemented with high pH-resulting outputs. H2 TPR profiles revealed a tailored stronger effect of Cu–Zn on Ga for process, operated with low pH-conditioned forms. Over Cu/ZnGaOX, WGS was sensitive to Cu, which was primarily active. Catalytic chemical reactivity, activity and selectivity were also found to be critically dependent on material lattice structure, copper surface area and metal–support interaction phenomena. The temperature-programmed surface reaction with mass spectrometry (TPSR–MS) measurements showed that formulations, synthesised at the pH of 8.0, enabled reaching >99% of the equilibrium yield CO conversion at 260 °C. An increase in the converted CO, oxidation and H2 productivity with the integral steam content in gaseous feed flow was achieved. The heterogeneous phase processing at the correlated pH of 7.6 demonstrated the highest formed CO product at the temperature of 200 °C, compared with literature. This is particularly promising for reagent purity hydrogen-fed fuel cells. The kinetics for each co-precipitated solid was evaluated regarding the efficiency for the WGS in a fixed bed reactor. Keywords: Syngas, Hydrogen, Cu/ZnGaOX catalyst, Water–gas shift (WGS), Steam reforming reactions, Fuel cell systems

V podporo razumevanju naravoslovnih pojmov in procesov na ravni delcev so v učna gradiva vključene različne predstavitve (reprezentacije). Članek se osredotoča na preučevanje, kako so submikroskopske reprezentacije (SMR-ji) integrirane v slovenske kemijske učbeniške komplete v povezavi z vsebinami učnega načrta za osnovno šolo. Izhodišče za analizo učbeniškega gradiva so predstavljali štirje holistični deskriptorji SMR-jev (direktni, indirektni, kombinirani deskriptor in SMR-ji brez deskriptorjev), ki glede na specifične opisnike SMR-jev do različne mere podpirajo učenca pri prepoznavanju informacijske vrednosti SMR-jev. Analiza učbeniških kompletov je pokazala, da se število SMR-jev močno spreminja glede na različne vsebine učnega načrta. Delež deskriptorjev, ki učencem omogočajo direktno prepoznavanje SMR-jev, je nizek v vseh vsebinah učnega načrta. Zanimivo je, da deskriptorji, ki ne omogočajo direktne prepoznave SMR-jev, prevladujejo v učbeniških kompletih. Z namenom pridobitve poglobljenega vpogleda v kriterije, na podlagi katerih avtorji učbenikov integrirajo SMR-je z različnimi deskriptorji v učbeniške komplete, so potrebne nadaljnje raziskave. To support the understanding of chemistry concepts and processes at the particulate level, various representations are included in learning materials. This paper focuses on how submicroscopic representations (SMRs) are integrated into Slovenian chemistry textbook sets with respect to the curriculum topics for 8th and 9th Grade. Textbook set analysis is based on four holistic SMRs descriptors (direct, indirect, combined descriptor, and SMRs without descriptors), which support learners’ recognition of SMRs’ informational value at different levels by providing different accompanying SMRs add-ons. The textbook sets analysis revealed that the number of SMRs varies significantly with regard to different curriculum topics. The overall proportion of the descriptors that enable the learner a direct recognition of SMRs is low in all curriculum topics. Interestingly, the descriptors that do not enable the learners a direct recognition of SMRs prevail in textbook sets. To obtain more detailed insight into the criteria based on which the textbook authors integrate SMRs with various descriptors into textbook sets, further studies are necessary.

Solvent- (SB) and water-borne (WB) fluoropolymer coatings were produced for the outdoor protection of bronze. The coatings were prepared from commercially available resins with alternating fluoroethylene/vinylether copolymers. Because any application of protective coatings on works of art requires that they be removable in accordance with conservation ethics, various approaches to achieve removability of coatings were tested. The influence of modifications was verified through comparisons of hydrophobic, compact and irremovable protective coatings. Consequently, we prepared four types of coatings: two SB coatings and two WB coatings. The first SB coating was designed to have a hydrophobic compact structure (SB-c coating), and the second SB coating was modified with the addition of agents that impart strippability (SB-h coating). The same approach was used for the preparation of the two WB coatings: a compact (WB-c) coating vs. a hydrophilic (WB-h) coating, the latter being prepared through the addition of hydrophilic polyisocyanate. The surface properties of the coatings were compared using scanning electron (SEM) and atomic force (AFM) microscopy. WB coatings were found to be more homogeneous in comparison with SB coatings and to have lower surface roughness. Contact angles confirmed the more hydrophobic nature of SB coatings. Potentiodynamic polarisation measurements and accelerated corrosion tests (exposure to acid vapours) revealed that protection efficiency not only increased with thickness but significantly depended on the coating structure. The structure of coatings depended on the rheological parameters of the formulations simulating their behaviour during storage, deposition, and formation of the dry coating. Combined electrochemical and vibrational spectroscopic experiments were used to simulate long-term outdoor exposure of the protective coatings. Ex situ IR RA spectroelectrochemical measurements showed that hydration was more prevalent with WB coatings, and oxidation of bronze at the interface eventually occurred (656 cm −1 band). WB coatings with more free C O groups were more prone to degradation. In situ Raman spectroelectrochemistry confirmed the better protection efficiency of SB over WB coatings. The optical properties of the coatings on glass showed higher transmittance for WB coatings compared to SB coatings.

Posljednji đerski i prvi pečuški tezarij Josipa Franje Domina, sastavljeni od 25 teza »iz eksperimentalne fizike«, a naslovljeni De corpore generatim, bili su prvi tezariji što ih je Zagrepčanin tiskao nakon što je objavio raspravu Dissertatio physica de aeris factitii genesi, natura, et utilitatibus (1784.), a izlažu jezgru prirodne filozofije u obliku nauka o ustroju tvari, temeljnim silama u prirodi i općim svojstvima tijelā, zatim mehaniku i nauk o gravitaciji te osnove kemije i astronomije. Tiskani u travnju 1785. i 1786. godine, oni označuju prijelomnicu u Dominovim prirodnofilozofskim gledištima. U đerskom tezariju 1785. Domin prvi put poimence spominje Boškovića i prvi put zadaje tezu o kemiji kao znanosti. Prvi spomen Boškovićeva prezimena podudara se s Dominovom transformacijom iz strogoga boškovićevca, kakav je bio u tezarijima od 1778. do 1784. godine, u prirodnoga fillozofa koji se nastoji izboriti za vlastite uvide. Teza o kemiji kao »znanosti podređenoj eksperimentalnoj fizici« svjedoči pak o utjecaju Dominova kompendija o kemiji plinova, ali je i programatski korak naprijed: »najjednostavnija počela« tijela Zagrepčanin naziva molekulama. U pečuškom tezariju 1786. Domin prvi put dodaje tezu o sili inercije, kamenu kušcu tadašnjih prirodnofilozofskih rasprava. Stoga oznaka »iz eksperimentalne fizike« s naslovnice tezarija ne znači da Domin isključuje prirodnu filozofiju iz svojih razmatranja, štoviše, ne znači da Domin prestaje biti filozofom prirode. Upravo obratno, kao »profesor teorijske i eksperimentalne fizike te mehanike kao i poljoprivrede« Domin se suočava s cijelim prirodnofilozofskim nasljeđem epohe, a glavni su mu sugovornici Newton, Bošković i dva boškovićevca: Leopold Biwald u Grazu i Ivan Krstitelj Horvath u Trnavi, Budimu i Pešti. Svoje stavove Domin ponekad oblikuje prema Boškovićevu tumačenju, ponekad s izričitim odmakom od Boškovića, a ponekad se vraća izvornom Newtonu., Two exam thesauri De corpore universim by Josip Franjo Domin, composed of 25 theses in the field of “experimental physics”, the last published in Györ in 1785 and the first published in Pecs in 1786, saw light soon after the printing of his treatise Dissertatio physica de aeris factitii genesi, natura, et utilitatibus (1784), and expounded the core of natural philosophy in the form of a doctrine of the structure of matter, fundamental forces in nature, and general properties of physical bodies, then mechanics and doctrine of gravitation, along with the basis of chemistry and astronomy. Being published in April 1785 and April 1786, they represent a turning­point in Domin’s views in natural philosophy. In the 1785 thesaurus, Domin for the first time mentions Bošković by name, and also for the first time proposes a thesis on chemistry as science. The first mention of Bošković’s surname corresponds with Domin’s transformation from a strict Boscovichian, as confirmed in the the sauri from 1778 to 1784, into a natural philosopher who comes forth with his own insights. The thesis on chemistry as “a science subordinated to experimental physics” is the fruit of Domin’s compendium on the chemistry of gases, yet, at the same time, is a programmatic step forward: Domin refers to “the simplest principles” of the bodies as molecules. In the 1786 thesaurus Domin introduces the thesis on inertia, touchstone of the then discussions in the field of natural philosophy. Therefore, “experimental physics” suggested in the thesauri title does not imply that Domin excluded natural philosophy from his considerations. Quite the reverse: as a “professor of theoretical and experimental physics, mechanics, and agriculture”, Domin is challenged by the legacy of the natural philosophy of the epoch, notably by Newton, Bošković and two Boscovichians – Leopold Biwald in Graz and Ivan Krstitelj Horvath in Tyrnau, Buda and Pest. Thus Domin either tends to mould his views in accordance with Bošković’s natural philosophy, or departs from Bošković or Boscovichians significantly, or shifts towards the natural philosophy of Newton.

The use of rare earth elements is a growing trend in diverse industrial activities, leading to the need for eco-friendly approaches to their efficient recovery and reuse. The aim of this work is the development of an environmentally friendly and competitive technology for the recovery of those elements from wastewater. Kinetic and equilibria batch assays were performed with zeolite, with and without bacterial biofilm, to entrap rare earth ions from aqueous solution. Continuous assays were also performed in column setups. Over 90% removal of lanthanum and cerium was achieved using zeolite as sorbent, with and without biofilm, decreasing to 70% and 80%, respectively, when suspended Bacillus cereus was used. Desorption from the zeolite reached over 60%, regardless of the tested conditions. When in continuous flow in columns, the removal yield was similar for all of the rare earth elements tested. Lanthanum and cerium were the elements most easily removed by all tested sorbents when tested in single- or multi-solute solutions, in batch and column assays. Rare earth removal from wastewater in open setups is possible, as well as their recovery by desorption processes, allowing a continuous mode of operation., This study was supported by the Portuguese Foundation for Science and Technology (FCT) under the scope of the research project PTDC/AAG-TEC/5269/2014, the strategic funding of UID/BIO/04469/2013 unit and BioTecNorte operation (NORTE-01-0145-FEDER-000004) funded by the European Regional Development Fund under the scope of Norte2020 - Programa Operacional Regional do Norte, Portugal., info:eu-repo/semantics/publishedVersion

Two-component solvent-born polyurethane coatings for the protection of bronze from corrosion were prepared. Trisilanol-heptaisooctyl polyhedral oligomeric silsesquixane (POSS) nanoparticles were exploited to increase the coating protective efficiency. Its improvement was confirmed through a combination of characterisation techniques. In particular, the POSS addition caused an increase of the water contact angle, and an enhancement of the elastic connotation and abrasion resistance of the polyurethane coating. Potentiodynamic polarisation measurements also indicated that the coating containing POSS nanoparticles has an improved protection efficiency. Impedance spectroscopy revealed that the magnitude of low-frequency impedance of polyurethane coatings decreased more for the coating without POSS during exposure in electrolyte for thirty days. Ex situ IR reflection-absorption spectroelectrochemistry was exploited to get insight into the degradation of coatings during chronocoulometric charging at anodic potentials. IR reflection-absorption technique was also used to evaluate any possible effect of different stripper solutions on the bronze substrate.

Chemical models are indispensable tool in chemistry class and enable secondary school pupils to develop complex thought processes and spatial concepts, both of which are necessary to improve their understanding of chemical concepts. In this research, special emphasis is given to complex competencies not only their acquisition, but rather how pupils develop them. For this purpose, a learning strategy has been developed, called learning by self-generating chemical models. Pupils learn individually on their own models, which are made from easily accessible, low-cost materials. The impact of workable models was investigated (assembly of commercial models and production of self-made models) on the (1) learning success using simple molecule shapes and (2) the degree of competence development which realized through the implemented activities. The study involved first-year secondary school-pupils, defined as self-creators of paper- and -wire models (experimental group) and assemblers of commercial models (called the control group). The appearance of the molecules being studied took the form of geometric shapes and structures, which pupils present by making of ball-, called wire-models from plasticine and wire or paper created, called paper models. Based on the results of statistical processing of the data, we found that self-creation of models (as an innovative approach) leads to better understanding and to subsequently sustained knowledge for the pupil. It should also be noted that pupils who were self-generators in comparisons to those who merely assembled the models, generally developed many complex skills in the areas of problem solving, practical competence, mathematical competence and critical thinking skills. The knowledge so acquired was also better understood.

The main aim of the teacher study program is to ensure the proper role of teaching practice, which is included in initial teacher training courses. It is necessary that teachers of chemistry gain or develop learner competencies for appropriate teaching/ learning in the chemistry subject by using innovative teaching methods. In terms of activities and methods correction of the continuous teaching practice model for prospective chemistry teachers in Pedagogical study program of 2nd degree "Educational Chemistry" which would ensure the creation of a competent chemistry teacher (active and innovative). The main result of the study is a list of potential competencies by prospective chemistry teachers using innovative teaching methods. These competencies can be developed and produced in the performance of activities defined by using continuous teaching practice, particularly in the areas of testing and assessment, experiential and collaborative learning, and experimental (laboratory and field) work. Each of these components is separately assessed by activity and competence.

Namen predstavljene raziskave je bil izboljšati učinkovitost učenja ob uporabi eksperimentalnega dela pri pouku kemije v slovenskih osnovnih šolah. Preučevali smo, kako se eksperimentalno delo izvaja pri rednem pouku kemije, in sicer je bilo posnetih 19 učnih enot rednega pouka kemije na 12 slovenskih osnovnih šolah, ki so bile naključno izbrane iz seznama šol iz celotne države. Skupno je bilo vključenih 332 osmošolcev, s povprečno starostjo 14,2 let. Učenci so bili posneti med poukom kemije, zbrani pa so bili tudi njihovi delovni listi, ki so jih reševali med eksperimentalnim delom. Z učitelji kemije, ki so izvedli pouk v teh šolah, so bili opravljeni intervjuji, prav tako so bili zbrane njihove učne priprave. Pridobljeni podatki so bili analizirani z uporabo kvalitativnih metod. Rezultati kažejo, da se mnogi učitelji v slovenskih osnovnih šolah v celoti ne zavedajo potenciala eksperimentalnega dela pri poučevanju kemije. Potrebne so nadaljne študije, s katerimi bo preučena vrednost različnih oblik izobraževanja v podporo učiteljem pri nadaljnem razvoju na področju uporabe eksperimentalnega dela pri pouku kemije. The aim of the research was to optimize the effectiveness of student learning based on experimental work in chemistry classes in Slovenian primary schools. To obtain evidence about how experimental work is implemented during regular chemistry classes, experimental work was videotaped during 19 units of chemistry lessons at 12 Slovenian primary schools from the pool of randomly selected schools. Altogether 332 eight-grade students were involved in the investigation, with an average age of 14.2 years. Students were videotaped during chemistry lessons, and their worksheets were collected afterward. The 12 chemistry teachers, who conducted lessons in these schools, were interviewed before the lessons their teaching plans were also collected. The collected data was analyzed using qualitative methods. The results indicate that many teachers in Slovenian primary schools are not fully aware of the potential of experimental work integrated into chemistry lessons for the development of students’ experimental competence. Further research of the value of different kinds of training to support teachers for the use of experimental work in chemistry teaching is needed.

V članku predstavljena raziskava se ukvarja s samo-evalvacijo napredka med praktičnim pedagoških usposabljanjem bodočih učiteljev kemije, študentov četrtega letnika, v primerjavi z mnenjem njihovih mentorjev na šoli. Vzorec sestavlja 21 bodočih učiteljev kemije in 21 njihovih mentorjev, izkušenih učiteljev kemije na osnovnih šolah. Za namen spremljanja razvoja bodočih učiteljev kemije med praktičnim pedagoških usposabljanjem so bodoči učitelji in njihovi mentorji izpolnjevali »Vprašalnik za spremljanje razvoja bodočih učiteljev kemije«, ki temelji na evalvaciji osmih karakteristik strokovnega razvoja učiteljev kemije. Rezultati kažejo, da so bili bodoči učitelji kemije v samo-evalvaciji bolj strogi od svojih mentorjev, še posebno po prvi izvedeni uri pouka kemije, medtem ko so bile ocene po zadnji izvedeni uri podobne z ocenami mentorjev glede večine ocenjevanih karakteristik. Podrobneje je predstavljen razvoj petih naključ no izbranih bodočih učiteljev kemije iz njihovega osebnega vidika, kakor tudi iz perspektive njihovih mentorjev. The research presented in this article deals with the self-evaluation of 4th year pre-service chemistry teachers’ progress during their second year practical pedagogical training in chemistry teaching at primary schools (students’ age 13–15 years) in comparison to the perception of their progress by their school mentors. The sample consisted of 21 pre-service teachers and 21 school mentors, in-service chemistry teachers, at primary schools. For the purpose of following to pre-service chemistry teachers’ development, the pre-service teachers as well as their mentors completed the “Questionnaire for monitoring students’ progress”, focusing on eight characteristics of professional development during practical pedagogical training. The results reveal that student-teachers were stricter in their self-evaluation in comparison to their school mentors after their first chemistry lecture at school during the practical pedagogical training however, after their last lecture, the evaluations were similar for most of the characteristics. The development of five randomly selected student- teachers is presented in detail from their own perspectives, as well as from their school mentors’ perspectives.

Densities of ethanol-water mixtures have been measured using a vibrating tube densimeter and a different arrangement high-pressure experimental set-up. Measurements were carried out at 298,15 K in a pressure range from 0.1 MPa to 5MPa. Partial molar volumes, excess molar volumes and coefficients of isothermal compressibility were calculated. The molar volumes of alcohol and its partial molar volumes in mixtures with water are found to decrease monotonously with increasing pressure. Excess molar volumes are negative at all pressures. The numerical P-V relations at each composition are correlated satisfactorily as a function of pressure by the Hayward equation. Gostote mešanic etanola z vodo smo izmerili z gostometrom, ki je bil prirejen za visokotlačne poskuse. Meritve so potekale pri 298,15 K v območju tlakov od 0,1 MPa do 5 MPa. Iz izmerjenih gostot smo izračunali parcialne molske prostornine, presežene molske prostornine in koeficiente izometrične stisljivosti. Molske prostornine etanola in njegove parcialne molske prostornine v mešanicah z vodo se monotono zmanjšujejo s povečanjem tlaka. Pri vseh tlakih so presežene molske prostornine negativne. Numerične P-V zveze v odvisnosti od tlaka so za vsako sestavo raztopine podane s Hayworthovo enačbo.

Traditional teaching does not often allow very active involvement of pupils in class. In chemistry and natural sciences in general experimental and laboratory work is one of the most effective methods for acquiring knowledge. Experimental work can also be exercised using virtual world. Virtual laboratory offers some important advantages. Understanding chemistry involves the ability of cognitive comprehension on three levels: the macroscopic level, the symbolic level and the level of particles where the virtual laboratory can be an effective tool. On this basis a didactic experiment was performed in order to verify the effectiveness of virtual laboratory from pupils' knowledge point of view. The experiment involved seventh grade pupils (N = 38). Furthermore, we tried to answer the question whether the learning results of pupils, according to the experimental design of classes using a virtual laboratory, are better than results gained through teaching classical science classes without visualization tools. The research of the didactic experiment carried out on a relatively small, pilot sample of pupils has shown that acquiring knowledge is more effective when using the virtual laboratory instead of classical teaching (in the case when classical approach does not include visualization elements crucial for learning and understanding chemistry). Tradicionalni pouk pogosto ne omogoča aktivnejše vloge učenca pri pouku. V kemiji in naravoslovnih vedah nasploh je eks­perimentalno in laboratorijsko delo eno izmed najučinkovitejših metod za pridobivanje znanja. Eksperimentalno delo lahko izvajamo tudi v virtualnem svetu. Virtualni laboratorij prinaša nekatere pomembne prednosti. Razumevanje kemije vključuje sposobnost razmišljanja na treh nivojih: makroskopskem nivoju, simbolnem nivoju in nivoju delcev, kjer kot učinkovito orodje lahko uporabimo virtualni laboratorij. Na tej osnovi smo izvedli didaktični eksperiment, da bi preverili učinkovitost uporabe virtualnega laboratorija, in sicer z vidika znanja učencev. V eksperiment so bili vključeni učenci 7. razreda (N = 38). Ob tem smo si zastavili vprašanje, ali so učni rezultati učencev po eksperimentalni zasnovi pouka z virtualnim laboratorijem boljši kot pouk naravoslovja brez vizualizacijskih elementov. Rezultati didaktičnega eksperimenta so pokazali, da je z vidika osvajanja znanja uporaba virtualnega laboratorija učinkovitejša kot pouk, kjer niso vključeni vizualizacijski elementi, ki so ključni pri učenju in razumevanju kemije.

Recent investigations have shown that modification of polymer matrix with filler and elastomers significantly affects composite's mechanical properties. Isotactic PP modified with either untreated or treated talc and either SEBS or SEBS-gMA were used in these investigations. Samples were prepared by melt-mixing in a Brabender kneading chamber and were compression molded into plates on a laboratory press. The composites were characterised by measuring mechanical properties (Young's modulus, yield stress, notched impact strength) and by defining morphology. Binary sistems PP/talc and PP/elastomer containing up to 16 vol.% of talc and up to 10 vol.% of elastomer, as well as ternary PP/talc/elastomer composites with 12 vol.% talc were investigated. Ternary composite's yield stress was also calculated by semiempirical equations. We have found out, that the use of treated modifiers (talc or elastomer) improves adhesion with matrix, which reflects on mechanical properties as better stress transfer. Novejše raziskave so pokazale, da lahko z modifikacijo polimerne matrike s polnilom in elastomerno fazo znatno vplivamo na mehanske lastnosti nastalega kompozita. V raziskavah smo uporabili izotaktični PP ter ga modificirali z neobdelanim oz. obdelanim talkom in SEBS oz. SEBS-gMA. Vzorce smo pripravili preko taline v Brabenderjevem gnetilniku in s stiskanjem v plošče na laboratorijski stiskalnici. Karakterizirali smo jih z merjenjem mehanskih lastnosti (Youngov modul, meja plastičnosti, zarezna udarna žilavost) in z opredelitvijo morfologije. Preučevali smo binarne sisteme PP/talk in PP/elastomer z vsebnostjo talka do 16 vol.% in do 10 vol.% elastomera, kakor tudi ternarne kompozite PP/talk/elastomer z 12 vol.% talka. Mejo plastičnosti ternarnih kompozitov smo določili še s polempiričnimi enačbami. Ugotovili smo, da uporaba obdelanih modifikatorjev (talka oz. elastomera) izboljša adhezijo z matriko, kar odseva na mehanskih lastnostih kot boljši prenos napetosti.

The present study is based on identification and elimination of several misconceptions of university level students regarding chemistry topics. For this reason, the static-group pre-test-post-test design was implemented with 52 teacher candidates. Regarding the content of the study, the experimental group participants opted for “Misconceptions in Science” course whereas the control group selected “Physics in environment” course in terms of elective courses. Data was collected through a form which consisted of 3 open-ended statements during the research process. In addition, an evaluation form was prepared to determine the opinions of the experimental group on the course. As a result of the study, the pre-test analyses revealed several misconceptions which all the participants have, whereas the post-test results indicated that “Misconceptions in science” course was effective in the elimination of experimental group’s misconceptions. Also, the course was found to be necessary and efficient. Delayed post-test results justified the resistivity of the misconceptions of the experimental group members, although they had been performing their jobs as in-service science teachers., Ovo istraživanje temelji se na prepoznavanju i eliminaciji nekih pogrešnih predodžbi studenata o području kemije. Zbog toga je primijenjen i proveden dizajn s predtestom i posttestom na statičnoj skupini na uzorku od 52 buduća nastavnika. Što se tiče sadržaja istraživanja, ispitanici u eksperimentalnoj skupini odabrali su kolegij Pogrešne predodžbe u prirodnim znanostima, a ispitanici u kontrolnoj skupini odabrali su kolegij Fizika u okolini kao svoj izborni kolegij. Za vrijeme istraživanja podaci su prikupljeni s pomoću obrasca koji se sastojao od 3 tvrdnje otvorenog tipa. Osim toga, pripremljen je evaluacijski obrazac da bi se ispitalo mišljenje sudionika u eksperimentalnoj skupini o kolegiju. Rezultat istraživanja dobiven je analizom predtesta s pomoću koje se prepoznalo nekoliko pogrešnih predodžbi koje su imali svi sudionici, a rezultati posttesta pokazali su da je kolegij Pogrešne predodžbe u prirodnim znanostima bio učinkovit pri eliminaciji pogrešnih predodžbi sudionika u eksperimentalnoj skupini. Također se pokazalo da je kolegij potreban i učinkovit. Rezultati posttesta koji je proveden s vremenskim odmakom potvrdili su ukorijenjenost pogrešnih predodžbi kod sudionika u eksperimentalnoj skupini, iako su oni već obavljali svoj posao nastavnika predmeta prirodnih znanosti.

U radu je prikazano kako je Tomo Mikloušić na kajkavskom jeziku popularizirao alkemiju i kemiju u hrvatskom društvu te pokazao njihovu vrijednost u praktičnoj uporabi. Time je prethodio utemeljenju hrvatske kemijske sredine u drugoj polovici 19. st. Rabio se pseudo-Geberovim djelov Summa, vrhunskim djelom europske alkemije, u njemačkom izdanju iz 1751. godine. Mikloušić je u svojem Izboru (1821.) opisao neke kemijske postupke uz korištenje alkemijskog nazivlja. To su postupak kositrenja (ozinyanya) posuđa cinjom, potom postupak korištenja tropa za ulje, oganj i potašu, priprava praha za podmazivanje peći, priprava boje za zid sa zelenim vitriolom, zatim priprava tzv. Sakssonskog sapuna za mazanje i lječenje bolnih udova, zglobova i natučenih mjesta te tzv. frankfurtskog crnila za tiskanje knjiga, bojanje drveta i drugo. Pionirski rad Tome Mikloušića na tom području potvrđen je time što se tekst sličnog sadržaja na hrvatskom jeziku pojavio tek ravno šezdeset godina kasnije (1881.) u knjizi Bogoslava Šuleka "Lučba za svakog ili popularna kemija".

straživanje medijskih priloga o kemiji u Međunarodnoj godini kemije, od 1. siječnja do 31. kolovoza 2011. godine, provedeno na pet hrvatskih dnevnih listova (Vjesnik, Večernji list, Jutarnji list, Slobodna Dalmacija i Novi list) i britanskom dnevniku The Guardian (oblika tzv. broadsheet) pokazuje velike razlike u medijskom tretmanu kemije. Frekvencija i raznolikost pristupa i načina, prije svega primjena konvergencije medija, tj. više medija istodobno u prezentaciji kemije u Guardianu neusporediva je s nevjerojatno malo članaka u našim dnevnim novinama. Na pronađenim primjerima diskutira se o vrijednostima vijesti za znanost u medijima, ali se ukazuje i na širu perspektivu za znanost u javnosti - na komunikaciju u popularnoj kulturi općenito, i to na primjeru popularne glazbe, kao i u aktivnostima kojima istraživači i istraživačke institucije nastoje doći u javnost. Ukazuje se na potpun nedostatak evaluacije postojećih programa susreta istraživača i građana i sugerira se potreba za promicanjem znanosti na različitim razinama.

As a recipient of the Annual Award for Science of the Republic of Croatia the lecturer has been invited to review his contributions to applications of topology to chemistry and material sciences.

Med je prirodan pčelinji proizvod složenoga kemijskoga sastava i zanimljivih fizikalnih i bioloških svojstava. Premda sadrži mikroorganizme u dormantnom stanju, odlikuje se snažnim antimikrobnim učinkom. Suvremena medicina sve obilnije koristi antimikrobna svojstva meda u terapiji rana različite etiologije, na primjer inficiranih kirurških rana i kroničnih venskih ulkusa. Sve brojnija klinička istraživanja izvještavaju o uspješnom korištenju medicinskih pripravaka meda u liječenju inficiranih rana kod kojih je prethodno neuspješno korištena antibiotska terapija. Premda su potrebna dodatna istraživanja, sasvim je jasno da će zbog odličnih rezultata, ekonomičnosti i zadovoljstva pacijenata uporaba meda u liječenju rana zauzimati sve istaknutije mjesto u medicinskoj praksi., Honey is a natural bee product, with complex chemical composition and interesting physical and biological properties. Although it contains dormant microbes, honey has strong antimicrobial effect. This effect is increasingly used in modem medicine for treating wounds of versatile etiology, for example infected surgical wounds and chronic venous ulcers. Numerous clinical trials have reported successful usage of medical-grade honey for treating infected wounds in which antibiotic therapy had previously been unsuccessful. Though additional research is needed, it is clear that the use of honey will take notable place in medical practice due to its excellent results, patient’s satisfaction and for being economic.

Kako bi se poboljšali pojedini aspekti obrazovanja, uvode se inovacije u obliku e-obrazovanja. Nastavni materijali dostupni su na internetu, a javljaju se i brojni programi obrazovanja na daljinu. Chemical Education Digital Library – ChemEd DL je poslužitelj koji okuplja materijale namijenjene obrazovanju u području kemije.

U radu je prikazana mrežna stranica Depth-First (http://depth-first.com) koja sadrži članke o kemijskim alatima i softverima, online informacijskim izvorima i općenitijim aktualnim temama iz područja kemije. Detaljnije je prikazan članak o 32 besplatne kemijske baze podataka na dostupne na internetu.

Obzirom na raskorak između na europskoj razini izražene potrebe za većim brojem stručnjaka u području prirodnih znanosti i tehnologije (okvirno: prirodoslovlja), te višim stupnjem opće razine prirodoznanstvene pismenosti, i opadanje interesa osnovnoškolaca za teme iz područja prirodoslovlja, prikazuju se struktura i karakteristike nekih nacionalnih okvirnih kurikuluma u području prirodoslovlja, kao jednog od čimbenika usvajanja znanja i vještina iz područja prirodoslovlja na razini obveznog obrazovanja. Iznose se rezultati komparativne analize kurikuluma za područje prirodoslovlja provedene u sklopu istraživačkog projekta Centra za istraživanje i razvoj obrazovanja Instituta za društvena istraživanja u Zagrebu, te ukazuje na možebitne smjerove usklađivanja hrvatskih nastavnih programa s tendencijama u europskim zemljama iz uzorka. Navode se i smjernice za konceptualizaciju hrvatskog kurikuluma za područje prirodoslovlja na osnovi koordiniranog kompetencijskog modela logičke razrade prezentacije sadržaja kao koraka prema ostvarivanju ovladavanja kompetencijama kao ishoda obrazovnog procesa., The article presents the structure of science curricula of different European countries as one of the factors contributing to development of coherent scientifi c knowledge and skills in compulsory education. It is the result of a wider research project conducted at the Institute for Social Research’s Centre for Educational Research and Development. The project included a comparative analysis of the said European curricular documents and development of recommendations for potential closer alignment of the Croatian national curricula with the perceived tendencies in the selected European countries. The recommendations focus on potential conceptualisation of the Croatian curriculum (in the fi eld of natural sciences) as a ‘deduction’ of the subjects’ content from a coordinated set of competences, which are defi ned as a general outcome of compulsory science education.

We give an explicit algorithm for computing the Szeged index of a graph which runs in ▫$O(mn)$▫ time, where ▫$n$▫ is the number of nodes and ▫$m$▫ is the number of edges. Dan je algoritem za računanje szegedskega indeksa grafa s časovno zahtevnostjo ▫$O(m,n)$▫, kjer je ▫$n$▫ število točk, ▫$m$▫ pa število povezav.

Properties of mixed-metal MOFs depend on the distribution of different metals within their frameworks. Determination of this distribution is often very challenging. Using an example of aluminum- and iron-containing MIL-100, we demonstrate that 27Al NMR spectroscopy, when combined with first-principles calculations and magnetic, X-band electron paramagnetic resonance, Fe K-edge extended X-ray absorption fine structure, and Mössbauer measurements, enables one to accurately determine the arrangement of Al and Fe within the metal trimers, which are the basic building units of MIL-100. In this particular material, the incorporation of Fe and Al on the framework metal sites is random. Crucial for deciphering the arrangement is detecting NMR signals, shifted because of the strong hyperfine interaction between the 27Al nuclei and the unpaired electronic spins of Fe3+ ions, assigning the shifted signals aided by first-principles calculations of hyperfine couplings, and quantitatively evaluating the NMR intensities and the measured effective magnetic moment.